docs: def find_single(decl_matcher, decls, recursive=True):
          """
          Returns a reference to the declaration, that match `decl_matcher`
          defined criteria.
  
          if a unique declaration could not be found the method will return None.
  
          :param decl_matcher: Python callable object, that takes one argument -
              reference to a declaration
          :param decls: the search scope, :class:declaration_t object or
              :class:declaration_t objects list t
          :param recursive: boolean, if True, the method will run `decl_matcher`
              on the internal declarations too
          """
          answer = matcher.find(decl_matcher, decls, recursive)
          if len(answer) == 1:
              return answer[0]